Atrial flutter with irregular ventricular response as a contraindication to digitalis.

ALTHOUGH atrial flutter occurs at atrial rates of 230 to 350 per minute, or faster, the ventricular response is usually at one half the atrial rate because of partial block of atrioventricular conduction. This block is of)hysiologic origin, arising from the refrac-tory period of the atrioventricular node, and it may occur without obvious cardiac disease .1-3 On the other hand, variations in the ventricular response during atrial flutter4 indicate increased block, which may be associated with disorders of the conduction system. Two cases are presented that illustrate the potential danger of produeing complete atrio-ventricular block by the use of digitalis in atrial flutter with greater than 2 :1 block and emphasize the value of an external electric cardiac pacemaker in ventricular asystole that may follow such comuplete block. Case Reports Case 1 iA 47-vear-old womnan with no history of cardio-va1sceulalr disease or hypertension was found on a routine examination to be in good health except for a grossly irregular rapid heart action. The pulse rate varied between 120 and 130, and the blood pressure was 120/80. The heart tones were of good quality, there were no iiiurniurs, and there were no signs of enlargement or failure. An electro-cardiogram (fig. 1) demonstrated atrial flutter with 2 :1 and 3 :1 ventricular response with Wenekebach phenomenon. The atrial flutter rate was approximately 300 and the ventricular rate 130.